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Summary
The liver – what it does
Your liver is one of the most important organs in your body.
It has a central role in digesting food and removing harmful substances. It breaks down nutrients into forms that are easier for your body to use. It also breaks down and removes waste products and substances that could be harmful.
It makes bile, which is a fluid that helps break down fats making it easier for your digestive system to process and absorb them. There is a network of bile ducts running through your liver. Bile helps moving waste products from your liver to your gallbladder and intestines for removal.
Your liver is connected to some important arteries and veins that bring blood into and out of your liver. Your liver also produces blood clotting factors, controls the amount of blood in your body, and stores vitamins and glycogen for energy. Importantly, your liver is a key component of your immune system removing potentially harmful bacteria and viruses from your body.
What are Liver Function Tests (LFTs)?
If your doctor suspects you may have liver problems, they will usually order Liver Function Tests (LFT)s. This is a standard group of tests, performed on the same blood sample, that check the health of your liver.
These tests measure enzymes and proteins that are either produced by the liver cells as part of its normal function or released into the blood when liver cells are damaged. Looked at together, along with your symptoms and medical history, they help build a picture of your liver’s health. Either higher or lower than normal levels of these substances can indicate a problem with your liver.
LFTs measure the enzymes aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and Gamma-glutamyl transferase (GGT) together with bilirubin (a substance produced when red blood cells break down and that is removed from the body by the liver), and albumin (the most common protein in your blood which is made by your liver).
What causes liver damage?
There are many different types of liver disease, and many health disorders can damage your liver. They include:
As your liver becomes damaged it becomes inflamed which causes scarring and stiffening. Your liver can become quite damaged before symptoms appear.
In the early stages of liver damage, there are often no symptoms or else mild non-specific symptoms, such as tiredness and nausea. As liver disease progresses your bile ducts can become blocked, and you may experience blood clotting problems.
In the early stages, scarring can be reversed. The liver is the only internal organ that can regrow itself and treatment and/or lifestyle changes can give the liver the time it needs to heal.
Eventually, there is so much scarring that it cannot be reversed and scar tissue replaces normal liver cells. This makes it harder for your liver to do its normal jobs. This increases the chance of cirrhosis (advanced liver disease) and eventually liver failure.
Why get tested?
Your doctors may order LFTs:
You may also have other blood tests at the same time to assess your general health such as:
Imaging tests that can show liver damage include ultrasound, CT (computerized tomography) and MRI (magnetic resonance imaging) scans. A liver biopsy may be done to help confirm a diagnosis and assess the extent of liver damage.
Acute and Chronic Hepatitis
Hepatitis is an inflammation of the liver. There are two major forms: acute and chronic.
| Acute Hepatitis | This is fast-developing and typically makes you feel very ill. In many cases, acute hepatitis causes jaundice - when skin and eyes become yellow and your urine turns brown. It is usually a short-term illness. Hepatitis A virus is the most common cause of acute hepatitis. It can also be caused by drugs, alcohol, immune system conditions and any condition that stops bile being released from your liver. Liver diseases that occur during pregnancy can cause acute hepatitis. |
| Chronic Hepatitis | This is when liver inflammation lasts longer than six months. It usually causes few or no symptoms - typically a loss of energy and tiredness. Most people don’t know that they have it. Chronic hepatitis gradually damages the liver, and this can slowly progress to fibrosis (scarring) and eventually to cirrhosis or liver failure. Chronic hepatitis is usually caused by hepatitis B or C infection but alcoholic liver disease (ALD) and metabolic-dysfunction fatty liver disease (MAFLD), are also major causes. |
Your liver and your bile ducts
The liver makes bile to help digest food and remove waste. Bile is a thick greenish fluid made in the liver cells. Once made, it flows through a network of ducts inside your liver, which transport it to your gallbladder for storage until you need to use it. Your gallbladder sits just underneath your liver.
When food (especially fats) enters the small intestine, the gallbladder releases bile which helps break down the fats into smaller droplets enabling it to be processed and absorbed by the intestine.
Bile is also important for removing waste and toxins. After your liver cells have broken them down, they pass into the bile ducts to be picked up by bile and transported to the gall bladder, then on to the intestines for removal. For more on this see bilirubin.
Scar tissue causes your liver to shrink and change shape, and this can cause your bile ducts to become blocked.
Having the test
Sample
Blood.
Any preparation?
None.
Your results
Reading your test report
Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
Liver Function Tests (For more information click through to the individual tests) Each of the LFTs gives different information about the way your liver is working. When looked at together the results can point to where the problem may lie and suggest what further tests you may need to confirm your diagnosis. | |
| Alanine aminotransferase (ALT) | ALT is an enzyme found mostly in the liver. Smaller amounts are also found in the kidneys, heart and muscles. Normally, ALT levels are low but when liver cells are damaged, they release ALT into the bloodstream. This usually occurs before more obvious symptoms of liver damage can be seen. A very high level of ALT is often seen with acute hepatitis. Moderate increases may be seen with chronic hepatitis. People with blocked bile ducts, cirrhosis and liver cancer may have ALT levels that are only moderately raised or close to normal. |
| Alkaline phosphatase (ALP) | ALP is an enzyme found throughout your body. The two main sources of ALP in your blood are your liver and bones. High levels of ALP can point to either liver disease or a bone disorder. If the levels of other LFTs are also raised, this usually indicates that you have liver problems. In particular, raised levels of both ALP and GGT indicate liver disease rather than bone disease. However, if other LFT levels are normal, this suggests that the ALP is coming from your bones. ALP may be very high if your bile ducts are blocked, if there is liver cancer or if you have bone disease. |
| Gamma- glutamyl transferase (GGT) | GGT is an enzyme found mainly in the liver and is normally only seen in low levels in the blood. When the liver is damaged or the flow of bile is obstructed, GGT level rises. It is therefore a useful test for detecting bile duct problems. A GGT test may be used to help decide the cause of a raised ALP. Both ALP and GGT are raised in bile duct and liver disease, but only ALP will be raised in bone disease. Increased GGT levels are also seen with alcohol overuse and often in people taking drugs such as carbamazepine and phenobarbitone. |
| Aspartate aminotransferase (AST) | AST is an enzyme which is mostly in the liver but also in red blood cells, heart and other muscles. When liver, red blood cells, heart or muscle cells are injured they release AST into the blood. A very high level of AST is often seen with acute hepatitis. AST may be normal to moderately increased with chronic hepatitis. In people with blocked bile ducts, cirrhosis, and liver cancer, AST concentrations may be moderately increased or close to normal. When liver damage is due to alcohol, AST often increases much more than ALT (this is a pattern seen with few other liver diseases). AST is also increased after heart attacks and with muscle injury. |
| Bilirubin | Bilirubin is an orange-yellow waste product that is made during the body's normal process of breaking down old red blood cells. It is processed by cells in your liver and picked up by bile which flows through a network of ducts inside your liver. It is transported to your intestines to be removed in the faeces. Bilirubin gives the stool its brown colour. If your liver is healthy only small amounts of bilirubin are found in your blood but if your liver isn't working properly bilirubin levels rise. High levels of bilirubin are the cause of jaundice – when your skin and the whites of your eyes become yellow. It is not uncommon to see high bilirubin levels in newborns whose livers have not yet fully developed. Bilirubin is increased in the blood when too much is being produced or too little is being removed due to bile duct obstructions, or to problems with bilirubin processing. |
| Albumin | Albumin is the main protein in the blood, and it helps carry hormones, vitamins, drugs and minerals such as calcium through the bloodstream. One of its most important roles is in helping to maintain fluid balance in the body by preventing fluid leaking from the blood vessels into other tissues. People who have chronic liver disease and kidney disorders are at risk of developing low albumin levels. This is due to lower production in the liver or too much being lost through damaged kidneys. Without enough albumin, fluid can build up in your lungs and other parts of your body. Although levels can be normal in early-stage liver disease, as damage worsens the liver is less able to produce enough albumin. Measuring albumin can help assess the severity of liver disease. |
Results of LFTs are usually assessed together. Several sets of results from tests performed over a few days or weeks are looked at together to see if there is a pattern. Your test results will typically change over time. It is possible to have abnormal results but not have liver disease. Many temporary conditions, such as shock, burns, severe infections, muscle trauma, dehydration, pancreatitis, haemolysis and pregnancy can cause one or more of the liver function tests to be abnormal. If you are taking medication that may affect your liver, abnormal test results may indicate a need to change the dosage or type of medication. | |
| Other tests you may have at the same time | |
| Total proteins | The total protein test measures albumin and all other proteins in blood, including antibodies. Total protein levels are often normal in liver disease. |
| Prothrombin Time (PT) | Prothrombin is a clotting factor made by the liver. It helps your blood to clot thereby preventing excessive bleeding. A prothrombin time (PT) test measures how long it takes for your blood to clot. If the test shows that your blood takes longer to clot than it should, it can be a sign of liver disease. |
| Further tests you may have | |
| Tests for infections | Viral infections especially hepatitis A, hepatitis B, or hepatitis C can damage the liver. |
| Antibody tests | Tests may be needed to look for the antibodies that are known to be linked to autoimmune liver disease. There are several forms of autoimmune liver disease. |
| Haemochromatosis tests | Iron overload and haemochromatosis can cause severe liver disease. If haemochromatosis is suspected, your medical team may request a full blood count (FBC), which gives information on the amount of haemoglobin in your blood, as well as the size and shape of the red blood cells, and iron studies, a group of tests that looks at the overall iron status in your body. If your results suggest haemochromatosis, an HFE genetic test may be ordered to make certain of the diagnosis. |
| Tests for inherited conditions | If your medical team thinks you may have an inherited condition called Wilson’s disease, the copper levels in your blood may be measured. It is important to tell your doctors of any family history of liver problems. |
Reference Intervals
Your results will be compared to reference intervals (sometimes called a normal range).
If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.
The reference intervals for all LFT's except GGT have common reference intervals which means that all laboratories in Australia should be using the same ranges for these tests.
| Reference intervals for LFTs (For more information click through to the individual tests) | |
| Alanine aminotransferase (ALT) | Female - 5 - 35 U/L Male - 5 - 40 U/L |
| Alkaline phosphatase (ALP) | Female and male 30 - 110 U/L (Children have higher levels) |
| Gamma- glutamyl transferase (GGT) | Female - 5 – 35 U/L Male - 5 – 50 U/L |
| Aspartate aminotransferase (AST) | Female - 5 - 30 U/L Male - 5 - 35 U/L |
| Bilirubin | 1-20 µmol/L |
| Albumin | Adult – 45 g/L |
| The reference intervals for the above tests are common reference intervals which means that all laboratories in Australia should be using this same target range. | |
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
More information
Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.
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